1. Prepare your scantron:
Use
a pencil,
not a pen!
Fill in your name and fill the bubbles under
your name.
LAST NAME FIRST, First name second
Put your 4-digit code instead of “IDENTIFICATION NUMBER”.
--- (The last 4 digits of your OleMiss ID.)
Test2 : Wednesday, Feb 27 – soon!
Question # 1: answer A
Question # 2: answer B
Question # 3: answer C
Setup:
Recall reading assignment
Chapter 6 (Telescopes): pp. 165 – 190
Please take a moment to mute your cell phone!

2. Review questions coming …

3. This question counts double!
sec 10 9 11 13 14 8 12 6 2 1 3 4 15 5 7 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22
Question 4
What is in the picture?
A A sunspot.
B A prominence.
C A solar flare.
D A filament.
Next question coming …

4. This question counts double!
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Question 5
Why are sunspots colder than the photosphere?
Because …
A they radiate off their heat more effectively than the photosphere.
B the magnetic field stops the convection.
C they are high up over the photosphere and high up it is cold.
D they have a different chemical composition.
Next question coming …

5. This question counts double!
sec 10 9 11 13 14 8 12 6 2 1 3 4 15 5 7 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22
Question 6
Where does the energy of a solar flare come from?
From …
A a nuclear explosion.
B electric discharge
C magnetic reconnection.
D matter falling into the Sun
E exceptionally hot rising bubbles reaching to the photosphere
Next question coming …

6. This question counts double!
sec 8 9 11 12 7 10 4 1 2 3 6 13 25 30 35 40 14 19 16 15 17 18 45 20 5
Question 7
Why is aurora very rare in Mississippi?
A Because the temperature is warm all year.
B Because aurora can be seen only in places with very dry climate.
C Because Mississippi is closer to the Moon than the Arctic or Antarctica.
D Because the magnetic field of Earth deflects charged particles.
E Because the Earth spins faster near the equator.

7. Astronomical telescopes
How do they work?
Use eyepiece to
watch image
Refractor:
Lens collects light
Use eyepiece to
watch image
Reflector:
Mirror collects light
2”-5” toy
6”-30” amateur
3’-10’ professional
10’-33’ super
Large lens/mirror collects much light -
the diameter of the telescope
is the important indicator!

8. Why do we need telescopes?
To collect much light
- need large diameter
To make small objects look large
- need magnification
Limits to light collection:
Diameter ~ 10 m (30 feet) will be too heavy to hold
Limits to magnification:
“Seeing” - stars jump around (related to twinkling)
- caused by air turbulence
little light
Notice:
all stars twinkle but planets twinkle less - why?
Answer:
planets are disks in a telescope,
but stars are always points
much light

9. Questions coming …

10. sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22
Question 8
Which of the following is the most important measure of a telescope?
A The magnification.
B The diameter of its mirror (or lens).
C The focal length of its mirror (or lens).
D The length of the telescope.
E The distance of the farthest object it can see.
Next question coming …

11. sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22
Question 9
The largest telescope we have at Ole Miss
is 15 inches. What category is that?
A Large professional.
B Average professional.
C A decent amateur size.
D A small amateur size.
E Uselessly small for astronomy.
Next question coming …

12. How large is the Big Dipper?
Angular sizes
How large is the Big Dipper?
250 apparent size
Stretch out your hand:
1 cm = 1o
25o
1o = 60 am (minute of arc)
1 am = 60 as (second of arc)
How large is the Moon?
1/2 0 apparent size
1/2o = 30 am = 1800 as
0.5o

13. Much more detail is visible
Resolution
Resolution of the human eye is 1 am = 60 as
Smallest visible detail is as small as this.
Stars are points in
all telescopes:
Calculated size of a star:
~ as,
Resolution of best telescope:
~ 0.1 as.
Much more detail is visible
Resolution of a simple telescope is ~ 1 as

14. The handle of the Big Dipper: the middle star is a double
Alcor and Mizar
Alcor
25 am
25 am
Mizar A & B
14 as
The handle of the Big Dipper:
the middle star is a double
How far apart are they?
25 am

15. Questions coming …

16. sec 8 9 10 12 11 7 6 1 2 3 4 13 30 35 40 45 14 25 16 15 18 17 19 20 5
Question 10
How do stars look in the largest telescope of the world?
A They look like large disks and we can see a
lot of detail on them.
B They look like large disks but there is not much detail to see,
although telescopes would have been able the resolve the details.
C They look like tiny disks but few or no details can be
seen on them.
D They look like points (no details visible).
E They look like “star-shaped” objects with rays
emanating from them.
Next question coming …

17. sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22
Question 11
How large does the Moon appear in the sky?
A A few inches.
B A few thousand miles.
C A few arc seconds.
D A light year.
E A half a degree.
Next question coming …

18. sec 10 9 11 12 15 14 13 8 7 1 2 3 5 4 6 16 26 17 27 28 30 29 24 25 23 19 18 20 21 22
Question 12
How large is the Big Dipper?
A A few miles.
B A few light years.
C Five million light years.
D More than twenty degrees.
E A half a degree.
Next question coming …

19. sec 10 9 11 13 14 8 12 7 2 1 3 4 6 5 15 17 26 25 27 28 30 29 16 24 19 18 23 20 22 21
Question 13
The two stars Alcor and Mizar are easily separated by the human eye.
This means that they must be farther apart than …
A a few degrees
B one arc minute.
C a few light years.
D a few million kilometers.
E a million light years.

20. Seeing : air moves  stars jump around and twinkle
• 2 to 4 arc seconds in Mississippi
• 1 arc second in good location
• 0.1 arc second on Mauna Kea, Hawaii
Size of “seeing”
Seeing limits magnification to a few hundred at best
Look at a double star in good and in bad weather:
Good
seeing
Bad
seeing